Hugh mccubdy spencer



Patented Oct 4, 1927.

UNITED] STATES PATENT OFFICE.

HUGE MUClJRDY SPENCER, F NEWARK, NEW JERSEY, ASSIGNOR T0 SEYDEL CHEMI- CAL COMPANY, A CORPORATION OF WEST VIRGINIA.

ALUMINA COAGULAN '1.

No Drawing.

This invention relates to the purification of liquids and solutions and particularly to the purification of water for industrial and municipal use and has for one, of its principal objects the more eflicient and convenient removal of suspended or colloidal matter from such liquids by means of an improved alumina containing coagulant or precipitating agent. Another object is to facilitate the efficient filtration, centrifugation, etc., of finely susp'fnded or colloidal solids or liquid:

7 in a liquid medium,

Hitherto in the purification of water by means involving the use of ,aluminum compounds; the usual practice has been to add the aluminum compound to the raw or treated water in the form of commercial aluminum sulfate or frequently as ordinary alum. If the water is Very alkaline copperas is also sometimes added, for the reason that the gelatinous precipitate of ferric hydroxide resulting from the action of the copperas on the water is less soluble in alkalinewatcis than is aluminum hydroxide, the ferric hydroxide taking the place of the portion of alumina redissolved by the excess alkali. After sufficient time has been allowed for the reaction between the aluminum compound and the alkalis of the water to take place, to produce a precipitate of hydrated alumina, the water is ordinarily filtered (bv methods already well-known in the art) whereby the precipitated alumina, along with the suspended and colloidal matter; 0mg- 85 inally present in the water is removed, producing a clarified water. If desired, the clarified water-from the filtering operation may then be subjected to any further suitable treatment, as with water softening 40 agents or sterilizing agents, septic tank treatment, or other suitable agencies to complete the purification all according to well known procedures.

The reaction between the aluminum salt and the bases in the water ordinarily requires a considerable length of time and for this reason storage tanks of irery large capacity are usually employed to permit storage of the water while the reaction is taking place 'andbefore passing the water to the filters.

If the raw water is acid it must be rendered alkaline before adding the su'lfateot' alumina, otherwise the hydrated alumlna will not be precipitated at all, or at least Application filed April 18, 1924. Serial No. 706,882.

ordinarily it will not be preci itated in suflic 1ent amounts to aid in the ltering operation to bring about an effective preclpitation of suspended and colloidal impurities. The

basic compounds ordinarily employed for neutralizing the acid of the raw waters to render them alkaline are lime, caustic soda or soda ash.

In all of these instances where an alumi num compound is employed as a coagulatmg or precipitating reagent, either alone or in connection with other reagents such as lime, copperas, etc., the reaction of the water before the addition of the aluminum compound must be carefully adjusted. That is to say, the raw water before treatment with the aluminum compound must either be alkaline to begin with or must be rendered so by the addition of suitable reagents as previously mentioned. On the other hand, a raw water which is originally too alkaline, or which has been rendered so by treatment, will retard the precipitation of the hydrated alumina and thus render the precipitating action of the aluminum salt less effective to a greater or less degree. This necessary preliminary treatment or control of the alkalinity of the raw water constitutes one of the most troublesome of the many serious difiiculties encountered in the application of alumina coagulants in the purification of water according to the methods hitherto in use and one of the principal objectsof the present invention is to provide an aluminacontaining coagulant which shall be effective in many instances where such preliminary treatment has hitherto been necessary in removin suspended and colloidal impurities from tie water without the necessity of subjecting the raw water to a preliminary treatment to control and regulate the alkaline reaction prior to the addition of the aluminacoagulant.

Also, as already mentioned, amon the other serious difliculties hitherto met with in the application of alumina-coagulants has men they nece sit it the Water (ll "rally to the cost a d in *on.-.n- Waters by this inctl. i i: the mriciiiniiiia or sscnine' of this dilicult}, constitutes a second rel-3 important oi'i 'ect my invention.

iilluise and other desirable objectires ar; accomplishcd in :u'cordancc "with the present ii'i'i'ci'ition in an economical and ci'in'i'enient- !l\tll11lt.l',i)l' 'oridinc' an aluniina-eontaining coagulant (it such character than when added in relatively small amounts to a relatively large Volume oi. Water, hydrated alumina is at once precipitated in a form which .arrics down the impurities with it and also which "an be readily removed by the usual method at iiltation and, turtluu'u'iore. this highly advantagrcous result attaiucduith a great variety of raw u: tors, industrial W ste liquors, L nd other liquids of Widely varying nature and cliaricteristics Without preliminary treatment.

lllore Spccll'lt'tlly, these advantageous results are accomplished by providing, in the preferred :torm of the invention. a concentrated alumina-containing' coagg ulant which is very nearly neutral or slightly acid in re action, and in. which thediydrated alumina is present, not in. a precipitated or gelatinous form as Would naturally be expected with neutralized or partially neutralized aluminum salts under ordinary circumstances, but in which it is present in a dissolved or partially dissolved state or colloidal condition from Which state it does not separate to any objectionable extent even when allowed to stand for considerable periods of time. ll hen, however, this improved coagulant is diluted to any considerable extent, as for example when it is added to the Water to be purified, the aluu'iina content. as mentioned, readily passes into the form of a gelatinous coagzium or precipitate carrying the suspended and colloidal impurities, bacteria, etc, along with it.

This action the more remarlnble since. as is Well known, when a solution containingan aluminum salt is gradually neutralized by caustic soda, for example to reduce the acidity of the solution, portion of the alumina.- in the solution will first separate (as the neutralizing; agent is added) in the form or"; a gelatinous precipitate or coagulum, and then completely re isolre as excess is added. in other Woros when this ordinary method of neutralizing or precipitating aiuminrwcontaining solutions is employed (as one would normally be led to practice) it is not possible or practicable to obtaii a partially or nearly neutralized or sligh l v acid aluminacontaining solution without, at

itatc of a e Liitlllli a content. aim-means oi 1 partially or 3 acid conceni uum compound preci ale portioi i ral ized or of z i a nu wit it obtaining air-J ohor coa ulatc at the as a certain neuirai :it is approached or iluiion remains or bc con mcchaui a a homogeneous in ch: rac t r (that. is, there is no objectionable prcciph hiion) and shows usually onl a slip'ht tur' buiity or milhincss due to the tornu. on ol hydra-led alumina in a highly disseminated or colloidal condition in the liquid.

'lhe reagent employed to produce this rcsuit in acrorda'm-c with til e present inrcu lion, may be a basic salt oi? a strong; base and a weal; acid. such 'l'or exanu'ile as sodium carbonate or bi-rarbtmatc or similar alkali metal carbonate or carbonate of ammonium. normal sodim-n sulphitc. li-sodium hydrogen phosphate, etc. By basic salt, in this conucctiou I mean a salt which has a sutlicicnlly stroiur basic strength to reduce the acidity' of a solution of an aluminum salt to thrdcrgrcc specified... in other words believe that the acid. of the basic saltv must be rcmust be capable ot peptiziugr the h uh alcd alumina but not strong enough to t'l)lllllltlll dissolve or chemically combine With the alumina to torm a stable compound therewith in solution or cause it to precipitate. 'ihe improved coagulant oi the invention may also be prepared by treatment at alumiuu'm hydroxide with such weal; acids, for exampha carbonic acid or sulturous acid, or by the anhydride of such Wfuh acids. Other pepiizing' agents which may be cutployci'l include sucrose. glucose, glycerol. ethyl alcohol and methyl alcohol.

ill will also be seen that the present invention in one (it its aspects provides tor the purification of water through the agency oi an alumiumi'i salt and, a basic compound, not by adding: the basic compound to the water prior to the treatment of the Water with the aluminum compound as in \hcusual methodisi'iiuti on the contrary, by providing for the addition oi the basic compound to a. concentrated solution containing the aluminum salt and then the addition of this mire tare to the water or solution to be purified.

One of the iu'iportant and unexpected advanta es obtained by this procedure, as alalumina. Another ad wntage is the elimination, in man instances, of the necessity of subectine acid waters to a neiuraliziuu I? t 7.

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treatment before adding the alumina-coagulant. The precipitation referred to occurs even when the water to be treated contains relatively large amounts of freeacid, sometimes as such as an amount chemically equivalent to the alumina-content of the coagulant although in this case precipitation might be somewhat retarded, whereas if the equivalent amount of base were first added to the water to neutralize the acid content thereof, in accordance with the older practice, the precipitation of hydrated alumina would frequently either not take place at all or else would be retarded to such an extent that long periods of time would be required to bring about the desired precipitation, with the accompanying disadvantages as to the storage tanks and time of treatment referred to above.

While I do-not wish to restrict the scope of my invention by any unwarranted assumption or explanations as to the exact chemical reactions or other changes which take place either during the preparation of my improved coagulant or during the action of the latter upon the water, nevertheless, I believe that the formation of the improved coagulant in accordance with the method of the present invention is due in part at least to a peptization or partial solubilization of the hydrated alumina precipitate or coagulum by the carbonic acid or other similar weak acid which isformed when the solution containing the aluminum salt is neutralized by sodium carbonate or like salt of a strong base and a weak acid. Also this is the explanation, I believe, of the fact for example that I may prepare my improved coagulant in one of its forms by first partially precipitating hydrated alumina from a solution of an aluminum salt by means of caustic soda and then passing carbon dioxide through the mixture thus obtained, or otherwise adding a suitable weakly acidic substance until the coagulated or precipitated hydrate of alumina 1S 'peptized or partially solubilized to produce a liquid containing the hydrated alumina in colloidal 0r partially solubilized condition such that when diluted it readily decomposes to again reproduce the precipitate or coagulum of hydrated alumina.

The formatiomof a satisfactory precipitate of hydrated alumina in accordance with the method of the present invention, even in the presence of free acid, is due also, -I believe, in part at'least to the dilution of the weak acid or other peptizing agent which is present in the coagulant in relatively high concentrations, in part to the slowness with which the precipitated or coagulated hydrated alumina reacts with the dilute solution ofacid already present in the water, and in part,. perhaps, to the relatively large change in the hydrogen ion concentration of the coagulant upon dilution. Another feature of the present invention which contributes to this same result is the greater ease with which the improved alumina-containing coagulant is hydrolyzed when diluted. The improved coagulant is adjusted with respect to its hydrolyzable properties in such a way that it is readily decomposed upon dilution to form a gelatinous precipitate of alumi' num hydroxide, whereas the salts, solutions and compounds hitherto used for this purpose, being more stable in their reaction toward water, are more difficult to hydrolyze or decompose in this manner.

Having described the main general features and characteristics of my invention, I wish now to give a few specific examples of my improved coagulant and methods of making and using the same. It is to be understood, however, that my invention is not restricted to the details given in these examples. but that they are given merely by way of illustrating a few embodiments of my in- "ention: i

Example 1. Run 240 pounds of water into a steam jacketed kettle that is lined with enamel or stoneware or any other substance that is not attacked by sulphate of alumina. Bring the water to a boil and add to it 286 pounds of commercial sulphateof alumina that is either iron free or not, as the'case may be. drinking water clarification. Stir until the sulphate of alumina has completely dissolved. Allow this solution to cool to room temperature, or else cool it artificially by pipe coils or by. admitting cold water into the jacket. Add, little by little and with constant stirring, 72 pounds of finely powdered commercial soda-ash. The soda-ash should not be added too quickly since this will cause too rapid frothing due to the decomposition of the soda-ash by the sulphate of alumina and the solution is apt to foam'over. Allow the solution to stand over night, after which it is ready for-use. i

The above formula may be varied by using the proportions of 800 parts water, 800 parts commercial sulphate of alumina, and 200 parts soda-ash. Also thesoda-ash may be dissolved in waterand the sulphateof alumina added in the pro ortions given in Example 1. However, this last method is troublesome because aluminum hydrate will not redisperse until practically all the soda has been neutralized and the solution has become acid. Hence the rule' to follow is to add the soda to the sulphate of aluminum and not vice versa. In conclusion it must be remembered that the amount of soda can be in any degree less than that given in Example 1, but it should not be much more than the amount indicated because if the solution crosses the iso-electric point precipitation of aluminum hydrate occurs which is The iron free is preferred for p pensionof aluminum hydroxide which is acidity not readily-redispersable unless the solution is again rendered acid by the addition of more sulphate of alumina. or some acid;

Example 2. Follow the procedure substantially as described in Example 1 substituting a suficient amount or normal sodium sulphite (Na SO for the sodium carbonate hydrogen phosphate (Na HPOJQH O) for p the sodium car 4 peptize or partially redissolve the precipi onate used in Example 1 to tate of hydrated alumina first formed to bring the alumina into substantially the same dispersed state or colloidal condition as in the end product of Example 1.

Example 4. To a solution consisting of 600 pounds of water and 400 pounds of commercial sulphate of alumina, add, with stirring, 120 pounds or calcium carbonate. Eilteror decent the liquid from any sediment. The clear solution is then ready for use. The stability of the resulting coagulant solution may be improved by the addition of from 5 to pounds of either NaHSO Na SO Na i-1P0 or NaH lP0 to the aluminum sulphate solution before the addition or the calcium carbonate. Exam le 5. Semi-solid, moist aluminum 'hydroxi e or aluminum hydrate suspended in water is subjectedto the action of a current or sulphur dioxide gas up to the limit of solubility of sulphur dioxide in the water present or'in an'ylesser amount that is found adequate to peptize or to put into a quasi solution (colloidal solution) the aluminum hydroxide; To promote the readiness of fprecipitation upon dilution, the

- the solution may bepartially neutralized by the addition or sodium carbonate. Any excess sulphurv dioxide gas may be recovered and returned to the pep-' tizing system containing the mixture or susbeing peptized by any suitable means.

Example. 6. Dissolve 200 pounds of AlJSO 1811-1 0 in 170 pounds or water,

and addlittle by little and with constant agitationiifi pounds of sodium, hydroxide while passing a stream or carbon dioxide gas up to the limit or solubility in the solution or in any lesseramountlthat is found ade- 9 'quate to peptize or put into a quasi solution (colloidal solution) the aluminum hydroxiide through the solution. Any excess carbon dioxide gas may-be recovered andreturned to'the peptizing system'by any conyenient means. a

neeaeea Example 7. Semi-solid, moist aluminum hydroxide or aluminum hydrate suspended in water is subjected to a current of mixed any' lesser amount that is round adequate to peptizeor to be put into a quasi solution (colloidal solution) the semi-solid aluminum hydroxide or the suspension of the aluminum hydroxide. Any excess of carbon dioxide or sulphur dioxide or both may be recovered and returned to the peptizing system containing the mixture, or suspension or semi-solid aluminum hydroxide which is being peptized by any convenient means,

Example 8 The peptizationof the alum:

ina or suspensionof aluminum hydrate no water may be efi'ected completely Orin part as described in Examples 4 or 6 and after wards the peptization may be completed sulphur dioxide may be employed up to saturation of the water present to act as a stabilizer ror'the, peptized aluminum hy-' droxide.

In Examples t to' 8 inclusive the carbon dioxide'or sulphur dioxide gas or both, may

in Examples 5 and, 7 in with sulphur dioxide gas, or an excess of droxide, ll may substitute the mineral baux I ite as such, preferably in finely comminuted state. In this manner it may avoid the nevces'sity or preparing the aluminum hydrox-.

I ide from a solution of aluminum salt, as for example by precipitation in the usual man ner. And in general it will be understood that m invention is not restricted to any particu ar methodof preparing the semisolid, moist aluminumhydroxide of the preceding examples', but ll may prepare this material by any other suitable method as for example by precipitating it from a solullli tion of aluminum sulphate or alum by means "of the requisite quantityor sodium carbonateior other suitable base under appropriate conditions or ll may prepare the semi-solid, moist aluminum hydroxide by precipitatin it from so-called, sodium aluminate 3 y means or any suitable acid under proper cpnditions all in accordance with methods and procedures which are well-known.

In -Examples 5 and 7 the semi-solid, moist aluminum hydrate may be in the form ofa ,jelly consisting 'of approximately 50% aluminum hydrate (Al(OH) and 50% water, v Furthermore, in each or. these examples vigorous stirring of the mixture may be employed during the gasifying process in order to promote the peptization.

It will be understood further that in the peptization of semi-solid,.moist aluminum hydrate or its equivalent, the peptization proceeds even in the'presence of impurities such as are formed during the process of preparing the semi-solid hydrate. Thus, for example, the peptization will take place in the presence of sodium sulphate formed when aluminum hydrate is precipitated from aluminum sulphate with caustic or carbonate of soda. Certain impurities, however, such as sodium sulphate, do have an effect, I have found, upon the stability of the peptized alumina or colloidal solution of aluminum hydroxide prepared in accordance with my invention. When, therefore, it is desirable to produce a stable form of my product I may separate such interfering impurities before or after peptizing the semisolid hydrate of alumina. Solid impurities, such as calcium sulphate, can be removed by filtration or decantation. Sodium sulphate may be removed by chilling.

Example 9. Dissolve 200 pounds of in 170 pounds of water and thoroughly stir into the solution about 1%, more or less, of sucrose, glucose or glycerol. To this solution add gradually and with constant stirring 38 pounds of sodium hydroxide. The peptizing reaction may be promoted, within limits, by warming the mixture during or just after the addition of the sodium hydroxide. Overheating,'however, must be avoided. Semi-solid moist aluminum hydroxide or aluminum hydrate, freshly precipitated in a separate operation, may be peptized in a similar manner immediately after precipitation. In the latter case, it is advantageous to use, in conjunction with the organic peptizing agent, some weakly acidic agent. a i

The above formula may be varied by using an equivalent amount of ethyl alcohol or methyl alcohol in place of sucrose, glucose or glycerol or mixtures of any or all of these reagents may be employed. Weakly acldlc substances such as-carbon dioxide, sulphur dioxide or sulphuric acid derivatives may also be employed in conjunction with the peptizing agents described in Example 9. Furthermore, in Example 9, I may acidify or make alkaline the solution or suspension during peptization by the addition of small amounts of mineral acids such as sulphuric acid, hydrochloric acid or nitric acidor by organic acids such as acetic or oxalic acid, or by alkaline substances such as sodium hydroxide, potassium hydroxide, ammonium hydroxide or tri-methyl-amine. I

Example. 10. Toa solution composed of 60 parts by weight of water and 40 parts by weight of crystallized aluminum sulphate is added about 1% by weight of sucrose, glucose or glycerol or an equivalent amount of ethyl alcohol or methyl alcohol or a mixture of any or all of these peptizing agents. To this solution is added in small quantities at a time an alkali or an alkaline salt such as sodium hydroxide, sodium carbonate, sodium sulphide, sodium oxide, lithium hyroxide, potassium hydroxide, or potassium carbonate or other substances which tends to neutralize the aluminum sulphate and to produce aluminum hydroxide, such as sodium phosphate, either the tri-sodium or the di-sodium phosphate, or sodium sulphite, until the alumina is brought into substantially the same dispersed state or colloidal condition as in the end product of Example 1.

In applying my improved coagulant prepared in accordance with the foregoing examples to the clarification of industrial waste I liquors, the amount which should be used varies considerably according to the character of the liquor bein treated and the amount of solid matter already present, but I have obtained good results in the clarification of certain waste-liquors by adding the peptized alumina prepared as described in Examples 1 to 3 in amounts corresponding to one-half of one percent to one percent by weight of the water or waste-liquors treated.

I claim:

1. An improved alumina-containing coagulant for clarifying aqueous liquids comprising a concentrated solution containing alumina and a solution of sulphur dioxide in an amount sufiicient to peptize the alumina.

2. An improved aluminacontaining coagulant for clarifying aqueous liquids comprising a concentrated solution containing alumina and sulphurous acid in an amount [sufficient to peptize the alumina.

3. An improved alumina-containing coagulant for clarifyin aqueous liquids comprising 'a concentrate solution containing alumina and peptizing agents in amount sufiicient'to peptize the alumina, the peptizing agent including a soluble acid-forming gaseous oxide and an organic peptizing agent.

4. The method of preparing an aluminacontaining coagulant for urifying aqueous liquids which comprises subjecting a hydrate of alumina to the peptizing action of sulphurous acid in the presence of Water.

5. The method of preparing an aluminacontainingcoagulant for clarifying aqueous solutions which comprises subjecting a hydrate of. alumina to the peptizing action of an organic peptizing agent and a soluble acid-forming gaseous oxide in the presence of water.

- 6. The method of purifying aqueous liquids to remove suspended impurities therefrom which comprises subjecting the liquid to the action of a concentrated solu I tion conteining a, hydrate of alumina which. 5 has been peptized by means of e sulphurous acid.

7. The method of urifying aqueous liquids to remove suspended impurities therefrom which comprises shbjecting the 10 liquid to the action of e concentrated soluneeneee therefrom by means of alumina Which co1n prises peptizing the alumina by m'eansof e su-lphurous acid in'the' presence of water and subsequently subjecting the aqueous liquid to the action of the concentrated'pep I tized alumina solution. 9. The method of purifying aqueous liquids to remove suspended impurities therefrom by means of en orgenic peptizing agent and a, soluble ecidforming gaseous oxide inthe presence ofweter end' 's'ubsequently subjecting the aqueous liquidate the notion of the concentruted peptized eluhxinesolution'l":

In testimon HU H McGURDY SPE GER.

I whereof I affix myi si I etureu 

